CRUD in CIS
06-09-2002, 07:29 AM
#1
Rennlist Member
Thread Starter
CRUD in CIS
It's no nuclear reactor, but I've got a "Clinch River Unidentified Deposit" problem in my car. It takes some explaining, so please feel free to skip this if you're not in the mood for a long story and some troubleshooting.
I've owned my '83 Euro 911SC for a little over a year. The car has around 75,000 total miles on it. I've driven the car around 5,000 miles without a problem, until now, except for a busted fuel gauge.
This spring, I removed the fuel tank to fix a dent. The dent was in the top and pushed down the fuel level sender to the point that it broke off. My best guess is that someone heavy kneeled on the tank to change the brake master cylinder. While the tank was out, I had a good look at as much of the inside of it as you can see through the drain and level sender openings, and it looked clean. After straightening the dent (with compressed air and a couple of gentle blows from a rubber hammer) and before reinstalling the tank, I did shake out a few flakes of rust/scale, which I didn't examine carefully.
I reinstalled the tank last week, threw in 6 gallons of fresh gas, and drove down to the gas station, where I added 20 gallons more. After around 10 miles of driving, the car began to miss at anything more than 1/4 throttle and 3,000 rpm. Next day, it didn't start or idle smoothly. It had a perfect cold start and idle before. I drove the car another 20 miles, or so, and the running got worse, though the car was still completely driveable around town. I suspected fuel contamination, removed the fuel filter and opened the canister for a look. What I found was rust contaminated fuel (fine particles). Also visible in the center section of the element were a few flakes of rust. But, the most alarming thing was that a steel end plate of the filter element had rusted out, and broken. This meant that the fuel was bypassing the filter, and that the very rust flakes from the busted end plate were journeying to my very sensitive CIS system!
Now for the recriminations - I didn't change the fuel filter last year, when I bought the car. So, I have no idea how old that element was. It is an unfamiliar (to me) brand - "Kayser." Of course, I did have on hand a new Mahle filter for that purpose, which I installed. After installing a new filter, the car ran better, but still missed over 3,000 rpm, at anything more than 1/4 throttle. It does have good throttle response, still, and drives around town great. I drove the car around 70 miles, and it still runs about the same, though the top end has probably fallen off even a little more.
Given the low miles on the car, I'm guessing that it has a small patch of corrosion from condensation as a result of sitting around so much. I'm pretty sure that the bottom of the tank is free of the rust you see from contaminated fuel. My best guess is that the rust is somewhere high and hard to see, like around the level sender opening or the vent line connection. I'll bet that there are a bunch of 911s out there with just as much corrosion in the tanks, but this doesn't show up, because they get filter changes and regular use and because the situation doesn't get destabilized by removing and banging the tank, like I did.
Finally, my questions. Has anyone had a similar problem, and if so what did they do? Where has the CRUD most likely accumulated? I am aware of the screens in the injectors. I have a thought that I might fix the problem by changing out the injectors (I have an extra set with very little use on them) and changing the fuel filter every 100 miles for a couple of weeks. Am I being too optimistic? Should I remove the tank and clean it by sloshing around gasoline, until it comes out clean? Do I need to remove the injection system and clean it as well as possible? What are the chances of damage to the control unit? Is there a standard procedure for cleaning a CIS system that's had this kind of contamination?
If I drain the tank for removal, does anyone have a suggestion about how to safely capture 3/4 of a tank (20 gallons, say) and to clean it for reuse? Should I just run through this tank of fuel and then drain it?
Thanks for reading this "book." Any help is greatly appreciated.
I've owned my '83 Euro 911SC for a little over a year. The car has around 75,000 total miles on it. I've driven the car around 5,000 miles without a problem, until now, except for a busted fuel gauge.
This spring, I removed the fuel tank to fix a dent. The dent was in the top and pushed down the fuel level sender to the point that it broke off. My best guess is that someone heavy kneeled on the tank to change the brake master cylinder. While the tank was out, I had a good look at as much of the inside of it as you can see through the drain and level sender openings, and it looked clean. After straightening the dent (with compressed air and a couple of gentle blows from a rubber hammer) and before reinstalling the tank, I did shake out a few flakes of rust/scale, which I didn't examine carefully.
I reinstalled the tank last week, threw in 6 gallons of fresh gas, and drove down to the gas station, where I added 20 gallons more. After around 10 miles of driving, the car began to miss at anything more than 1/4 throttle and 3,000 rpm. Next day, it didn't start or idle smoothly. It had a perfect cold start and idle before. I drove the car another 20 miles, or so, and the running got worse, though the car was still completely driveable around town. I suspected fuel contamination, removed the fuel filter and opened the canister for a look. What I found was rust contaminated fuel (fine particles). Also visible in the center section of the element were a few flakes of rust. But, the most alarming thing was that a steel end plate of the filter element had rusted out, and broken. This meant that the fuel was bypassing the filter, and that the very rust flakes from the busted end plate were journeying to my very sensitive CIS system!
Now for the recriminations - I didn't change the fuel filter last year, when I bought the car. So, I have no idea how old that element was. It is an unfamiliar (to me) brand - "Kayser." Of course, I did have on hand a new Mahle filter for that purpose, which I installed. After installing a new filter, the car ran better, but still missed over 3,000 rpm, at anything more than 1/4 throttle. It does have good throttle response, still, and drives around town great. I drove the car around 70 miles, and it still runs about the same, though the top end has probably fallen off even a little more.
Given the low miles on the car, I'm guessing that it has a small patch of corrosion from condensation as a result of sitting around so much. I'm pretty sure that the bottom of the tank is free of the rust you see from contaminated fuel. My best guess is that the rust is somewhere high and hard to see, like around the level sender opening or the vent line connection. I'll bet that there are a bunch of 911s out there with just as much corrosion in the tanks, but this doesn't show up, because they get filter changes and regular use and because the situation doesn't get destabilized by removing and banging the tank, like I did.
Finally, my questions. Has anyone had a similar problem, and if so what did they do? Where has the CRUD most likely accumulated? I am aware of the screens in the injectors. I have a thought that I might fix the problem by changing out the injectors (I have an extra set with very little use on them) and changing the fuel filter every 100 miles for a couple of weeks. Am I being too optimistic? Should I remove the tank and clean it by sloshing around gasoline, until it comes out clean? Do I need to remove the injection system and clean it as well as possible? What are the chances of damage to the control unit? Is there a standard procedure for cleaning a CIS system that's had this kind of contamination?
If I drain the tank for removal, does anyone have a suggestion about how to safely capture 3/4 of a tank (20 gallons, say) and to clean it for reuse? Should I just run through this tank of fuel and then drain it?
Thanks for reading this "book." Any help is greatly appreciated.
06-09-2002, 08:19 AM
#2
If it was me I'd clean as much as possible, as far as the gas currently in the tank I'd drive until its nearly empty, hoping that it's sloshing around would continue to "clean" the tank. I'm not sure about porsches but other cars I've worked on had a screen on the pickup in the tank, you might try cleaning it as well. Perhaps and a can of fuel system cleaner to this tank before running it. If I had any real concerns it would be that these particles may damage the pump or fuel distributer. If you really want to clean the gas that's in the tank I'd buy some gas cans and transfer the gas to them, then let them sit like settling tanks until all the crude deposits on the bottom, from there poor off the clean gas on top into other cans. Either way I'd be willing to bet your whole fuel system is a mess, dismantling it and cleaning everything would be the best bet.
06-09-2002, 05:02 PM
#4
Rennlist Member
If your tank is as crudded up as you indicate, I suggest you drain all the gas and take it to a reputable tank cleaner and sealer company and have the source cleaned up and protected with appropriate sealants. From there I would proceed downstream cleaning all the other possible collection areas. Without cleaning the source, you'll never get rid of the problem. Do it right once!!
Spider911
88 Carrera
Spider911
88 Carrera
06-09-2002, 05:41 PM
#5
Intermediate
Join Date: Apr 2002
Location: Germany
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I went through this just a few months ago...what a PITA!!! I had to treat my tank...1 week project at least, and replace the fuel filter and fuel pump. Once all this was done, a tank of Chevron with Techron cleaned out the system pretty well and I have had no problems since. I did ask around at the time and was told that is rust had been pushed into the mixture control unit, than that would be bad to the note of $800.00 OUCH!! If you search the posts, you will find a quick step by step guide I posted for another member.
06-10-2002, 01:30 AM
#6
RL Technical Advisor
Hi Tom:
Boy, I'm sure sorry to hear of your fuel system troubles. This situation is not uncommon when proper maintenance has been ignored as the CIS is VERY sensitive to dirt & rust.
Having been down this road a few times, here's what I've done. I'm assuming that the fuel filter was indeed corrupted and allowed all manner of rust particles and dirt downstream to the rest of the system.
1) R&R'ed the fuel tank. I placed 5 lbs of #4 steel shot in there and spent 35 minutes hand-shaking the living crap out of it to loosen the rust and scale inside. Then I flushed it out with clean solvent, cleaned the steel shot in a colander and repeated the whole process.
2) The tank was then taken to a specialist to be cleaned and internally coated.
3) The injectors, WUR and FD were removed and all lines blown with clean dry air. Injectors were tested with the special Bosch fixture for that purpose and any that didn't clean up were replaced. The WUR was flushed, as well.
4) Personally, I've had no luck cleaning the FD. I wish it were not so, but those things have VERY tiny passages that are simply inaccessible and cannot be really cleaned out. You might get lucky but you should know that if you cannot clean it, whatever rust or dirt still in there will contaminate your cleaned or new injectors. Nowadays, I simply save myself the aggravation (and customer's time) and install a rebuilt one.
Given what's at stake, its cheaper in the long run for the customer.
Finally, don't forget the in-tank filter and make sure the main filter is changed at least every 5K miles. Its really cheap insurance, given what you'll spend here.
I hope this is useful.
Boy, I'm sure sorry to hear of your fuel system troubles. This situation is not uncommon when proper maintenance has been ignored as the CIS is VERY sensitive to dirt & rust.
Having been down this road a few times, here's what I've done. I'm assuming that the fuel filter was indeed corrupted and allowed all manner of rust particles and dirt downstream to the rest of the system.
1) R&R'ed the fuel tank. I placed 5 lbs of #4 steel shot in there and spent 35 minutes hand-shaking the living crap out of it to loosen the rust and scale inside. Then I flushed it out with clean solvent, cleaned the steel shot in a colander and repeated the whole process.
2) The tank was then taken to a specialist to be cleaned and internally coated.
3) The injectors, WUR and FD were removed and all lines blown with clean dry air. Injectors were tested with the special Bosch fixture for that purpose and any that didn't clean up were replaced. The WUR was flushed, as well.
4) Personally, I've had no luck cleaning the FD. I wish it were not so, but those things have VERY tiny passages that are simply inaccessible and cannot be really cleaned out. You might get lucky but you should know that if you cannot clean it, whatever rust or dirt still in there will contaminate your cleaned or new injectors. Nowadays, I simply save myself the aggravation (and customer's time) and install a rebuilt one.
Given what's at stake, its cheaper in the long run for the customer.
Finally, don't forget the in-tank filter and make sure the main filter is changed at least every 5K miles. Its really cheap insurance, given what you'll spend here.
I hope this is useful.
